A semiautomatic rifle, which has a pivoting, opening/closing barrel and in which are generically provided a cartridge feeding means on one side and a means for ejecting a fired cartridge case from below, was described in a contemporary patent application of the same applicant. Besides advantages in terms of safety and use practicality, such a semiautomatic rifle has the significant feature of being ambidextrous thanks to the ejection from below, which does not influence the right and left raising of the gun.